AbstractThe purposes of this study were: (i) to evaluate the association of sit-to-stand (STS) power and body composition parameters [body mass index (BMI) and legs skeletal muscle index (SMI)] with age; (ii) to provide cut-off points for low relative STS power (STS_rel), (iii) to provide normative data for well-functioning older adults and (iv) to assess the association of low STS_rel with negative outcomes. Cross-sectional design (1369 older adults). STS power parameters assessed by validated equations, BMI and Legs SMI assessed by dual-energy X-ray absorptiometry were recorded. Sex- and age-adjusted segmented and logistic regression analyses and receiver operator characteristic curves were used. Among men, STS_rel showed a negative association with age up to the age of 85 years (− 1.2 to − 1.4%^year−1; p < 0.05). In women, a negative association with age was observed throughout the old adult life (− 1.2 to − 2.0%^year−1; p < 0.001). Cut-off values for low STS_rel were 2.5 W kg⁻¹ in men and 1.9 W kg⁻¹ in women. Low STS_rel was associated with frailty (OR [95% CI] = 5.6 [3.1, 10.1]) and low habitual gait speed (HGS) (OR [95% CI] = 2.7 [1.8, 3.9]) in men while low STS_rel was associated with frailty (OR [95% CI] = 6.9 [4.5, 10.5]) low HGS (OR [95% CI] = 2.9 [2.0, 4.1]), disability in activities of daily living (OR [95% CI] = 2.1 [1.4, 3.2]), and low quality of life (OR [95%CI] = 1.7 [1.2, 2.4]) in women. STS_rel declined with increasing age in both men and women. Due to the adverse outcomes related to STS_rel, the reported cut-off points can be used as a clinical tool to identify low STS_rel among older adults.